1. Field of the Invention
The present invention relates to combinational circuits, and particularly to a method for synthesizing soft error tolerant combinational circuits.
2. Description of the Related Art
Due to current technology scaling trends, digital designs are becoming more sensitive to radiation-induced particle hits resulting from radioactivity decay and cosmic rays. A low-energy particle can flip the output of a gate, resulting in a soft error if it's propagated to a circuit output.
Reliability with respect to soft errors has become a critical issue in digital circuits. In the past few decades, CMOS technology has reached high scaling advancement. This advancement is consistent with Moore's law, which states that the number of transistors that can be placed in a chip doubles every 18 months. As CMOS technology is improving and reaching the nanometer scale, quantum mechanical effects come into the picture, generating many challenges for additional scaling of CMOS devices. This has motivated researchers to investigate new technologies for circuit design. Circuits and devices based on nanotechnology-based fabrication are expected to offer extra density and performance that takes electronic circuits to the next higher integration level.
Nanoelectronics can operate at very high frequencies (of the order of THz) and achieve very high densities (1012 devices per cm2). Several researchers have presented novel successful nanoelectronic devices. These devices include carbon nano-tubes (CNT), silicon nano-wires (NW), and quantum dot cells. Nanoscale devices are limited by several characteristics. The most dominant characteristics are the devices' higher defect rates and increased susceptibility to soft errors. These limiting characteristics are due to the inherent randomness and imprecision in the bottom-up manufacturing process, which results in a large number of defective devices during the fabrication process. Moreover, the reduced noise tolerance of these devices is responsible for inducing device malfunctions by external influences, such as EMI (electromagnetic interference), thermal perturbations, and cosmic radiation.
In general, errors can be categorized as either permanent or transient errors. Permanent (hard) errors may occur during the manufacturing process or during the lifetime of a device. Transient (soft) errors can arise due to multiple sources, such as high-energy particles, coupling, power supply noise, leakage, and temporal circuit variations. The transient error can last for one or many clock cycles. Both types of errors affect the circuit reliability, if they aren't tolerated. Reliability of a circuit can be defined as the ability to function properly despite the existence of such errors. It is desired to improve tolerance against permanent and transient errors in order to enhance circuit reliability.
Thus, a method for synthesizing soft error tolerant combinational circuits solving the aforementioned problems is desired.